You remove the WaitingScreen here because it's only single message deletion, this action "should" be  fast but it's not actually. We will update the threadlist first and update the threadUI page in the async callback. The message will stay on UI in a while after user click the delete(especially the threadlist is long). Maybe we can:
1) Only update the threadlist when latest message is deleted.
2) Show WaitingScreen if we really need to update threadlist
Wdyt?